1. Field of the Invention
The present invention relates to a wireless sensor network system, and more particularly, to a terminal node device which is synchronized with a sink node device to constitute a server-based wireless sensor network or is not connected to a sink node device to constitute an independent sensor network and a wireless sensor network system which is configured so as to improve reliability and utilizability by using the terminal node device.
2. Description of the Related Art
A wireless sensor network technology is a core technology for implementing ubiquitous computing environments, where a large number of nodes may be connected in a wireless manner to be operated.
In the sensor network, since each node is operated with a battery having a limited capacity, measured data need to be transmitted by using minimum energy. In addition, in order to adapt the sensor network to a real-time application system, transmission delay in a large-scale sensor network needs to be minimized. Therefore, in a sensor network which needs to be monitored at real time, a protocol which minimizes consumption of a battery and has small network transmission delay is required.
Due to these requirements, inventors of the present invention filed Korean Patent Publication No. 10-2008-0070966, titled “Wireless Sensor Network Having a Linear Structure capable of performing Bidirectional Data Communication and a Method thereof” in the Korean Intellectual Property Office
The above-mentioned application discloses a technique of a wireless sensor network which is configured with a plurality of nodes, wherein each node is connected to one upper node and one lower node so that nodes from a sink node to a terminal node are linearly connected, wherein each node includes an active duration for communicating data with the upper node and the lower node, wherein the active duration includes a downlink active duration for transmitting data/command from the sink node to the terminal node and an uplink active duration for transmitting data/command from the terminal node to the sink node to implement bidirectional communication between the sink and terminal nodes in one period of the active duration.
Since the above-described wireless sensor network is configured as a time-synchronization-based linear network, the sink node is necessarily installed. Therefore, in the case where the sink node is in disorder, there is a problem in that the whole wireless sensor network cannot be operated. Therefore, there is a problem in that the sink node needs to be controlled for continuous network maintenance.
On the other hand, wireless sensor networks have been widely commercialized so as to detect a forest fire, a symptom of bridge breakage, a damage of cultural assets and to be used for intelligent buildings or small-sized buildings. Therefore, in order to solve the above-described problems, development of techniques for improving utilizability of the wireless sensor network is required.